10,733 research outputs found
VHE gamma ray absorption by galactic interstellar radiation field
Adopting a recent calculation of the Galactic interstellar radiation field,
we calculate the attenuation of the very high energy gamma rays from the
Galactic sources. The infra-red radiation background near the Galactic Center
is very intense due to the new calculation and our result shows that a cutoff
of high energy gamma ray spectrum begins at about 20 TeV and reaches about 10%
for 50 TeV gamma rays.Comment: 6 pages, 1 figure, figure is changed, conclusion not change
Muon anomalous magnetic moment and lepton flavor violation in MSSM
We give a thorough analysis of the correlation between the muon anomalous
magnetic moment and the radiative lepton flavor violating (LFV) processes
within the minimal supersymmetric standard model. We find that in the case when
the slepton mass eigenstates are nearly degenerate, , coming from
SUSY contributions, hardly depends on the lepton flavor mixing and, thus, there
is no direct relation between and the LFV processes. On the
contrary, if the first two generations' sleptons are much heavier than the 3rd
one, i.e., in the effective SUSY scenario, the two quantities are closely
related. In the latter scenario, the SUSY parameter space to account for the
experimental is quite different from the case of no lepton
flavor mixing. Especially, the Higgsino mass parameter can be either
positive or negative.Comment: 22 pages, 9 figures; Some discussions are modifie
Prognostic Importance of Circulating Tumor Cells in Nonsmall Cell Lung Cancer: A Prospective Study
Purpose: To investigate the prognostic value of circulating tumor cells (CTCs) and to predict the treatment response in a non-small cell lung cancer (NSCLC).Methodology: A single-center prospective study involving 93 patients with NSCLC was conducted. Blood samples were analyzed for CTC count before and after chemotherapy. Clinical relevance of CTCs with patient`s characteristics and treatment response were determined.Results: Higher levels of CTCs were associated with severe stage of NSCLC (p = 0.003), tumor histology (p = 0.014) and metastases (p = 0.013). Significant difference in CTC count was observed in favorable (CTCs < 5) and unfavorable (CTCs ≥ 5) groups. Progression-free survival (PFS) was 5.8 months (range: 5.32 to 6.43) and 2.2 months (range: 1.85 to 3.01) in the favorable and unfavorable groups, respectively (HR: 3.88, 95% CI, p < 0.001). Similarly, overall survival (OS) was 7.3 months (95% CI, 6.51 to 7.92) and 3.9 months (95% CI, 1.99 to 5.13), respectively (HR: 4.8, 95% CI, p < 0.001). Multivariate regression analysis revealed CTCs as strong predictors of OS and PFS. Significant reduction (p < 0.001) in CTC count was also observed after one cycle of chemotherapy.Conclusion: Patients with low CTC count live longer and remain progression-free for a longer period of time than those with high CTC count. High CTCs can be detected in severe forms of lung cancer and can be used as a valid prognostic marker. However, this assertion requires validation in larger prospective clinical cohorts.Keywords: Circulating tumor cells, Non-small cell lung cancer, Circulating tumor cell, Prognosi
The influence of internal corporate governance mechanisms on capital structure decisions of Chinese listed firms
Purpose: This paper examines the effects of internal corporate governance mechanisms on the capital structure decisions of Chinese listed firms.
Design/Methodology: Using a large and more recent dataset consisting of 2386 Chinese listed firms over the period from 1998 to 2012, we employ panel data and use different statistical methods (OLS, fixed effects, and system GMM) to analyse the effects of firm-specific and corporate governance influences on capital structure.
Findings: We find that the proportion of independent directors and ownership concentration exert significant influence on the level of Chinese long-term debt ratios after controlling for firm-specific determinants and split share reforms. Further analysis separating our sample into state-owned enterprises (SOEs) and privately- owned enterprises (POEs) suggests that ownership concentration in the hands of the state leads to decrease in debt ratios.
Implications: The finding implies that concentrated ownership in the hands of the state appears more efficient compared to their private counterparts in their monitoring role.
Original Value: This study extends prior literature, which has concentrated disproportionately on firm-specific influences on capital structure, to the effects of within-firm governance mechanisms on capital structure decisions. The paper contributes to the agency theory-capital structure discourse in an emerging country context where corporate governance system appears weak
Tailoring cations in a perovskite cathode for proton-conducting solid oxide fuel cells with high performance
© 2019 The Royal Society of Chemistry. A rational design of a high-performance cathode for proton-conducting solid oxide fuel cells (SOFCs) is proposed in this study with the aim of improving the hydration properties of conventional perovskite cathode materials, thus leading to the development of new materials with enhanced proton migration. Herein, potassium is used to dope traditional Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF), which is demonstrated to be a beneficial way for improving hydration, both experimentally and theoretically. The theoretical study was needed to overcome practical limits that hindered direct hydrogen mobility measurements. The novel material Ba0.4K0.1Sr0.5Co0.8Fe0.2O3-δ (BKSCF) shows a lower overall proton migration energy compared with that of the sample without K, suggesting that K-doping enhances proton conduction, which shows an improved performance by extending the catalytic sites to the whole cathode area. As a result, a fuel cell built with the novel BKSCF cathode shows an encouraging fuel cell performance of 441 and 1275 mW cm-2 at 600 and 700 °C, respectively, which is significantly higher than that of the cell using the pristine BSCF cathode. This study provides a new and rational way to design a perovskite cathode for proton-conducting SOFCs with high performance
The Temporal and Spectral Characteristics of "Fast Rise and Exponential Decay" Gamma-Ray Burst Pulses
In this paper we have analyzed the temporal and spectral behavior of 52 Fast
Rise and Exponential Decay (FRED) pulses in 48 long-duration gamma-ray bursts
(GRBs) observed by the CGRO/BATSE, using a pulse model with two shape
parameters and the Band model with three shape parameters, respectively. It is
found that these FRED pulses are distinguished both temporally and spectrally
from those in long-lag pulses. Different from these long-lag pulses only one
parameter pair indicates an evident correlation among the five parameters,
which suggests that at least 4 parameters are needed to model burst
temporal and spectral behavior. In addition, our studies reveal that these FRED
pulses have correlated properties: (i) long-duration pulses have harder spectra
and are less luminous than short-duration pulses; (ii) the more asymmetric the
pulses are the steeper the evolutionary curves of the peak energy () in
the spectrum within pulse decay phase are. Our statistical
results give some constrains on the current GRB models.Comment: 18 pages, 7 figures, accepted for publication in the Astrophysical
Journa
Evaluation of energy-distribution of a hybrid microbial fuel cell-membrane bioreactor (MFC-MBR) for cost-effective wastewater treatment
© 2015 Elsevier Ltd. A low-cost hybrid system integrating a membrane-less microbial fuel cell (MFC) with an anoxic/oxic membrane bioreactor (MBR) was studied for fouling mitigation. The appended electric field in the MBR was supplied by the MFC with continuous flow. Supernatant from an anaerobic reactor with low dissolved oxygen was used as feed to the MFC in order to enhance its performance compared with that fed with synthetic wastewater. The voltage output of MFC maintained at 0.52 ± 0.02 V with 1000 Ω resister. The electric field intensity could reach to 0.114 V cm-1. Compared with the conventional MBR (CMBR), the contents rather than the components of foulants on the cake layer of fouled MFC-MBR system was significantly reduced. Although only 0.5% of the feed COD was translated into electricity and applied to MBR, the hybrid system showed great feasibility without additional consumption but extracting energy from waste water and significantly enhancing the membrane filterability
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